SM+5520+Oil+and+Grease

OIL & GREASE (5520)/Introduction

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5520 55 20 OI OIL L AND GREA GREASE SE**

5520 55 20 A. Int Intro rodu duct ction ion In the deter determinat mination ion of oil and grease grease,, an absolu absolute te quantity of  a specific sub substa stance nce is not measured. measured. Rather, Rather, gro groups ups of sub sub-stance sta ncess wit with h sim simila ilarr phy physic sical al char charact acteri eristi stics cs are det determ ermine ined d quanti qua ntitat tative ively ly on the bas basis is of the their ir com common mon sol solubi ubilit lity y in an organic extracting solvent. “Oil and grease”   is defined as any materi mat erial al rec recove overed red as a subs substan tance ce sol solubl ublee in the solvent. solvent. It includes other material extracted by the solvent from an acidi fied samplee (such as sulfu sampl sulfurr compou compounds, nds, certain organic dyes, and chlorophyll) and not volatilized during the test. The 12th edition  Standard Methods prescribed the use of petroleum ether as the of  Standard solvent for natural and treated waters and  n -hexane for polluted waters. water s. The 13th edition added tric trichloro hlorotri trifluor uoroet oethan hanee as an optional solvent for all sample types. In the 14th through the 17th

* Approved by Standard Methods Committee, 2001. Joint Task Group: John Gute (chair), Jennifer R. Calles, Lavern V. Tamoria.

editions, only trichlorotri fluoroethane was specified. However, because of envir environment onmental al probl problems ems associ associated ated with chlorofluorocarbons, an alternative solvent (80%  n -hexane and 20% methyl-tert -butyl -butyl ether ether)) was included for gravi gravimetri metricc metho methods ds in the 19th edition. In the 20th editi edition, on, trichlorotri trichlorotrifluoroe uoroethane thane was dropped from all gravimetric procedures (retained for 5520C, an infrared method), and replaced with  n -hexane. Solvent-recovery techniques techni ques were inclu included ded and solven solventt recyc recycling ling was stron strongly gly recommended. In the methods given below, the 80% n-hexane and 20% methyl-tert -butyl -butyl ether solvent mix has been dropped from 5520B, D, and E, and an alternative to the liquid/liquid extraction extra ction procedure procedure using solid-phase solid-phase adsorb adsorbent ent disks is included. It is important to understand that, unlike some constituents that represent distinct chemical elements, ions, compounds, or groups

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AGGREGATE ORGANIC CONSTITUENTS (5000)

of compounds, oils and greases are defined by the method used for their determination. In detailed studies involving wastewaters and solid matrices, it was shown that  n -hexane produced results statistically different from results produced by trichlorotri fluoroethane.1,2 Trichlorotrifluoroethane may at some point be prohibited entirely by regulatory authorities. EPA currently recommends use of  n -hexane in place of trichlorotrifluoroethane.3 The methods presented here are suitable for biological lipids and mineral hydrocarbons. They also may be suitable for most industrial wastewaters or treated ef fluents containing these materials, although sample complexity may result in either low or high results because of lack of analytical specificity. The method is not applicable to measurement of low-boiling fractions that volatilize at temperatures below 85°C. 1.   Significance

Certain constituents measured by the oil and grease analysis may influence wastewater treatment systems. If present in excessive amounts, they may interfere with aerobic and anaerobic biological processes and lead to decreased wastewater treatment ef ficiency. When discharged in wastewater or treated ef fluents, they may cause surface films and shoreline deposits leading to environmental degradation. A knowledge of the quantity of oil and grease present is helpful in proper design and operation of wastewater treatment systems and also may call attention to certain treatment dif ficulties. In the absence of specially modified industrial products, oil and grease has two primary components: fatty matter from animal and vegetable sources and hydrocarbons of petroleum origin. The portion of oil and grease from each of these two major components can be determined with Method 5520F. A knowledge of the relative composition of a sample minimizes the dif ficulty in determining the major source of the material and simplifies the correction of oil and grease problems in wastewater treatment plant operation and stream pollution abatement. 2.   Selection

of Method

For liquid samples, four methods are presented: the liquid/  liquid partition-gravimetric method (B), the partition-infrared method (C), the Soxhlet method (D), and the solid-phase, partition-gravimetric method (G). Method C is designed for samples that might contain volatile hydrocarbons that otherwise would be lost in the solvent-removal operations of the gravimetric procedure. Method D is the method of choice when relatively polar, heavy petroleum fractions are present, or when the levels of  nonvolatile greases may challenge the solubility limit of the solvent. For low levels of oil and grease (10 mg/L), Method C is the method of choice because gravimetric methods do not provide the needed sensitivity. Method G can be used as an alternate to Method B to reduce solvent volumes and matrix problems. Method E is a modi fication of the Soxhlet method and is suitable for sludges and similar materials. Method F can be used in conjunction with Methods B, C, D, or G to obtain a hydrocarbon measurement in addition to, or instead of, the oil and grease measurement. This method makes use of silica gel to separate petroleum hydrocarbons from the total oil and grease on the basis of polarity.

3.   Sample

Collection, Preservation, and Storage

Collect a representative grab sample in a wide-mouth glass bottle that has been washed with soap, rinsed with water, and finally rinsed with solvent to remove any residues that might interfere with the analysis. As an alternative to solvent rinsing, cap bottle with aluminum foil and bake at 200 to 250°C for at least 1 h. Use PTFElined caps for sample bottles; clean liners as above, but limit temperature to 110 to 200°C. Collect a separate sample for an oil and grease determination. Do not overfill the sample container and do not subdivide the sample in the laboratory. Collect replicate samples for replicate analyses or known-addition QA checks. Collect replicates either in rapid succession, in parallel, or in one large container with mechanical stirring (in the latter case, siphon individual portions). Typically, collect wastewater samples of approximately 1 L. If sample concentration is expected to be greater than 1000 mg extractable material/L, collect proportionately smaller volumes. If analysis is to be delayed for more than 2 h, acidify to pH 2 or lower with either 1:1 HCl or 1:1 H 2SO4 and refrigerate. When information is required about average grease concentration over an extended period, examine individual portions collected at prescribed time intervals to eliminate losses of grease on sampling equipment during collection of a composite sample. In sampling sludges, take every possible precaution to obtain a representative sample. When analysis cannot be made within 2 h, preserve samples with 1 mL conc HCl/80 g sample and refrigerate. Never preserve samples with CHCl3  or sodium benzoate.

4.   Interferences

a. Organic solvents have the ability to dissolve not only oil and grease but also other organic substances. Any fi lterable solventsoluble substances (e.g., elemental sulfur, complex aromatic compounds, hydrocarbon derivatives of chlorine, sulfur, and nitrogen, and certain organic dyes) that are extracted and recovered are defined as oil and grease. No known solvent will dissolve selectively only oil and grease. Heavier residuals of  petroleum may contain a significant portion of materials that are not solvent-extractable. The method is entirely empirical; duplicate results with a high degree of precision can be obtained only by strict adherence to all details. b. For Methods 5520B, D, E, F, and G, solvent removal results in the loss of short-chain hydrocarbons and simple aromatics by volatilization. Significant portions of petroleum distillates from gasoline through No. 2 fuel oil are lost in this process. Adhere strictly to sample drying time, to standardize gradual loss of  weight due to volatilization. For Methods 5520B, D, E, F, and G, during the cooling of the distillation  fl ask and extracted material, a gradual increase in weight may be observed, presumably due to the absorption of water if a desiccator is not used. For Method 5520C use of an infrared detector offers a degree of selectivity to overcome some coextracted interferences ( ¶ 4a   above). For Methods 5520D and E, use exactly the specified rate and time of  extraction in the Soxhlet apparatus because of varying solubilities of different greases. For Method 5520F, the more polar hydrocarbons, such as complex aromatic compounds and hydrocarbon derivatives of chlorine, sulfur, and nitrogen, may be adsorbed by the silica gel. Extracted compounds other than hydrocarbons and fatty matter also interfere.

OIL & GREASE (5520)/Liquid-Liquid, Partition-Gravimetric Method

c.  Alternative techniques may be needed for some samples if  intractable emulsions form that cannot be broken by centrifugation. Such samples may include ef fluents from pulp/paper processing and zeolite manufacturing. Determine such modifications on a case-by-case basis. d.   Some sample matrices can increase the amount of water partitioned into the organic extraction  fl uid. When the extraction solvent from this type of sample is dried with sodium sulfate, the drying capacity of the sodium sulfate can be exceeded, thus allowing sodium sulfate to dissolve and pass into the tared  fl ask. After drying, sodium sulfate crystals will be visible in the  fl ask. The sodium sulfate that passes into the  fl ask becomes a positive interference in gravimetric methods. If crystals are observed in the tared  fl ask after drying, redissolve any oil and grease with 30 mL of extraction solvent and drain the solvent through a funnel containing a solvent-rinsed  fi lter paper into a clean, tared  fl ask. Rinse the fi rst fl ask twice more, combining all solvent in the new flask, and treat as an extracted sample. e.  Silica gel  fi nes may give positive interferences in 5520F if  they pass through the  fi lter. Use  fi lters with smaller pores if this occurs with a particular batch of silica gel.

5520 B. 1.

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 f.   Analyte recovery may be compromised unless efforts are made to ensure uniform sample passage through the solid-phase extraction disks used in Method 5520G.

5. References 1. U.S. ENVIRONMENTAL  P ROTECTION  A GENCY. 1993. Preliminary Report of EPA Efforts to Replace Freon for the Determination of Oil and Grease, Revision 1. EPA-821-R-93-001, U.S. Environmental Protection Agency, Washington, D.C. 2. U.S. ENVIRONMENTAL PROTECTION  A GENCY. 1995. Report of EPA Efforts to Replace Freon for the Determination of Oil and Grease and Total Petroleum Hydrocarbons: Phase II. EPA-821-R-95-003, U.S. Environmental Protection Agency, Washington, D.C. 3. U.S. ENVIRONMENTAL PROTECTION AGENCY. 1998. Method 1664. Revision A, n-Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated n-Hexane Extractable Material (HEM; Non-polar material) by Extraction and Gravimetry. EPA821-R-98-002, U.S. Environmental Protection Agency, Washington, D.C.; 40 CFR Part 136, Table IB, Item 41 (July 1, 2000); Federal Register   64:93, 26315.

Liquid-Liquid, Partition-Gravimetric Method

  General Discussion

Dissolved or emulsified oil and grease is extracted from water by intimate contact with an extracting solvent. Some extractables, especially unsaturated fats and fatty acids, oxidize readily; hence, special precautions regarding temperature and solvent vapor displacement are included to minimize this effect. Organic solvents shaken with some samples may form an emulsion that is very dif ficult to break. This method includes a means for handling such emulsions. Recovery of solvents is discussed. Solvent recovery can reduce both vapor emissions to the atmosphere and costs. 2.   Apparatus

a. Separatory funnel, 2-L, with TFE* stopcock. b. Distilling  fl ask , 125-mL. c. Liquid funnel, glass. d. Filter paper , 11-cm diam.† e. Centrifuge,  capable of spinning at least four 100-mL glass centrifuge tubes at 2400 rpm or more.  f. Centrifuge tubes, 100-mL, glass. g. Water bath, capable of maintaining 85 °C. h. Vacuum pump  or other source of vacuum. i. Distilling adapter  with drip tip. Setup of distillate recovery apparatus is shown in Figure 5520:1. Alternatively, use commercially available solvent recovery equipment.  j. Ice bath.

Figure 5520:1. Distillate recovery apparatus.

k. Waste receptacle, for used solvent. l. Desiccator. 3.   Reagents

* Te flon or equivalent. †  Whatman No. 40 or equivalent

a. Hydrochloric or sulfuric acid , 1:1: Mix equal volumes of  either acid and reagent water.

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b.  n- Hexane, 85% minimum purity, 99% minimum saturated C6 isomers, residue less than 1 mg/L; distill if necessary. Do not use any plastic tubing to transfer solvent between containers. c. Sodium sulfate, Na2SO4, anhydrous crystal. Dry at 200 – 250°C for 24 h. d. Acetone, residue less than 1 mg/L. e. Hexadecane, 98% minimum purity.  f. Stearic acid , 98% minimum purity. g. Standard mixture, hexadecane/stearic acid   1:1 w/w, in acetone at 2 mg/mL each. Purchase prepared standard mixture, or prepare as follows.1 Place 200  2 mg stearic acid and 200  2 mg hexadecane in a 100-mL volumetric  fl ask and  fi ll to mark with acetone. N OTE: The solution may require warming for complete dissolution of  stearic acid. After the hexadecane and stearic acid have dissolved, transfer solution to a 100- to 150-mL vial with TFE-lined cap. Mark  solution level on the vial and store in dark at room temperature. Immediately before use, verify level on vial and bring to volume with acetone, if required. Warm to redissolve all visible precipitate. NOTE: If there is doubt of the concentration, remove 10.0  0.1 mL with a volumetric pipet, place in a tared weighing pan, and evaporate to dryness in a fume hood. The weight must be 40  1 mg. If not, prepare a fresh solution. 4.   Procedure

AGGREGATE ORGANIC CONSTITUENTS (5000)

time, but first rinse sample container with each solvent portion. Repeat centrifugation step if emulsion persists in subsequent extraction steps. Combine extracts in tared distilling  flask, and include in flask a final rinsing of  filter and Na2SO4 with an additional 10 to 20 mL solvent. Distill solvent from  flask in a water bath at 85°C. To maximize solvent recovery, fit distillation flask with a distillation adapter equipped with a drip tip and collect solvent in an ice-bathcooled receiver (Figure 5520:1). When visible solvent condensation stops, replace bent distillation apparatus with vacuum/air adapter connected to vacuum source. Immediately draw air through flask  with an applied vacuum for the  final 1 min. Remove  flask from bath and wipe outside surface to remove moisture. Cool in desiccator until a constant weight is obtained. To determine initial sample volume, either  fi ll sample bottle to mark with water and then pour water into a 1-L graduated cylinder, or weigh empty container and cap and calculate the sample volume by difference from the initial weight (assuming a sample density of 1.00). 5.   Calculation

Calculate oil and grease in sample as follows: mg oil and grease/L 

r 

V 

s

where: total weight of  fl ask and residue, minus tare weight of  flask, mg, and V   initial sample volume, L.

W 

r 

When a sample is brought into the laboratory, either mark sample bottle at the water meniscus or weigh the bottle, for later determination of sample volume. If sample has not been acidified previously (see Section 5520A.3), acidify with either 1:1 HCl or 1:1 H2SO4   to pH 2 or lower (generally, 5 mL is suf ficient for 1 L sample). Using liquid funnel, transfer sample to a separatory funnel. Carefully rinse sample bottle with 30 mL extracting solvent and add solvent washings to separatory funnel. Shake vigorously for 2 min. Let layers separate. Drain aqueous layer and small amount of  organic layer into original sample container. Drain solvent layer through a funnel containing a  filter paper and 10 g Na2SO4, both of  which have been solvent-rinsed, into a clean, tared distilling  fl ask  containing boiling chips. If a clear solvent layer cannot be obtained and an emulsion of more than about 5 mL exists, drain emulsion and solvent layers into a glass centrifuge tube and centrifuge for 5 min at approximately 2400 rpm. Transfer centrifuged material to an appropriate separatory funnel and drain solvent layer through a funnel with a filter paper and 10 g Na2SO4, both of which have been prerinsed, into a clean, tared distilling flask. Recombine aqueous layers and any remaining emulsion or solids in separatory funnel. For samples with 5 mL of emulsion, drain only the clear solvent through a funnel with pre-moistened  fi lter paper and 10 g Na 2SO4. Recombine aqueous layers and any remaining emulsion or solids in separatory funnel. Extract twice more with 30 mL solvent each

W 



s

6.   Precision

and Bias

Method B was tested in a single laboratory study and an interlaboratory method validation study.1 Combined data from these studies yielded an average recovery of 93% and precision (as relative standard deviation) of 8.7%. 7. Reference 1. U.S. ENVIRONMENTAL PROTECTION  A GENCY. 1998. Method 1664, Revision A.  n -Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated n -Hexane Extractable Material by Extraction and Gravimetry. EPA-821-R-98-002; 40 CFR Part 136 (July 1, 2000); Federal Register   64 (93):26315. U.S. Environmental Protection Agency, Washington, D.C.

8. Bibliography KIRSCHMAN, H.D. & R. POMEROY. 1949. Determination of oil in oil fi eld waste waters.  Anal. Chem.   21:793. U.S. ENVIRONMENTAL PROTECTION AGENCY. 1995. Report of the Method 1664 Validation Studies. EPA-821-R-95-036, U.S. Environmental Protection Agency, Washington, D.C.

OIL & GREASE (5520)/Partition-Infrared Method

5520 C. 1.

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Partition-Infrared Method

  General Discussion

a. Principle:  The use of trichlorotri fluoroethane as extraction solvent allows absorbance of the carbon-hydrogen bond in the infrared to be used to measure oil and grease. Elimination of the evaporation step permits infrared detection of many relatively volatile hydrocarbons. Thus, the lighter petroleum distillates, with the exception of gasoline, may be measured accurately. With adequate instrumentation, as little as 0.2 mg oil and grease/L can be measured. b. De finitions:  A  “known oil” is defined as a sample of oil and/or grease that represents the only material of that type used or manufactured in the processes represented by a wastewater. An “unknown oil”  is defined as one for which a representative sample of  the oil or grease is not available for preparation of a standard. 2.   Apparatus

a. Separatory funnel, 2-L, with TFE* stopcock. b. Volumetric fl ask,  100-mL. c. Liquid funnel,  glass. d. Filter paper,  11-cm diam.† e. Centrifuge,  capable of spinning at least four 100-mL glass centrifuge tubes at 2400 rpm or more.  f. Centrifuge tubes,  100-mL, glass. g. Infrared spectrophotometer,  double-beam, recording. h. Cells,  near-infrared silica.

Shake vigorously for 2 min. Let layers separate. Drain all but a very small portion of the lower trichlorotrifluoroethane layer through a funnel containing a  fi lter paper and 10 g Na2SO4, both of which have been solvent-rinsed, into a clean, 100-mL volumetric flask. If a clear solvent layer cannot be obtained and an emulsion of more than about 5 mL exists, see Section 5520B.4. Extract twice more with 30 mL solvent each time, but  fi rst rinse sample container with each solvent portion. Repeat centrifugation step if emulsion persists in subsequent extraction steps. Combine extracts in volumetric  fl ask, and include in  fl ask a  fi nal rinsing of  filter and Na2SO4   with an additional 10 to 20 mL solvent. Adjust  fi nal volume to 100 mL with solvent. Prepare a stock solution of known oil by rapidly transferring about 1 mL (0.5 to 1.0 g) of the oil or grease to a tared 100-mL volumetric  flask. Stopper flask and weigh to nearest milligram. Add solvent to dissolve and dilute to mark. If the oil identity is unknown (5520C.1b) use the reference oil (5520C.3d ) as the standard. Using volumetric techniques, prepare a series of standards over the range of interest. Select a pair of matched near-infrared silica cells. A 1-cm-path-length cell is appropriate for a working range of about 4 to 40 mg. Scan standards and samples from 3200 cm1 to 2700 cm1 with solvent in the reference beam and record results on absorbance paper. Measure absorbances of samples and standards by constructing a straight base line over the scan range and measuring absorbance of the peak maximum at 2930 cm1 and subtracting baseline absorbance at that point. If the absorbance exceeds 0.8 for a sample, select a shorter path length or dilute as required. Use scans of standards to prepare a calibration curve.

3.   Reagents 5.   Calculation

a. Hydrochloric acid, HCl, 1  1. b. Trichlorotri fl uoroethane (1,1,2-trichloro-1,2,2-trifluoroethane), boiling point 47°C. The solvent should leave no measurable residue on evaporation; distill if necessary. Do not use any plastic tubing to transfer solvent between containers. c. Sodium sulfate,  Na 2SO4, anhydrous, crystal. Dry at 200 to 250°C for 24 h. d. Reference oil:   Prepare a mixture, by volume, of 37.5% isooctane, 37.5% hexadecane, and 25.0% benzene. Store in sealed container to prevent evaporation. 4.   Procedure

Refer to Section 5520B.4 for sample handling and for method of dealing with sample emulsions. After carefully transferring sample to a separatory funnel, rinse sample bottle with 30 mL trichlorotrifluoroethane and add solvent washings to funnel. * Te flon or equivalent. †  Whatman No. 40 or equivalent.

mg oil and grease/L 

 A



1000

mL sample

where:  A



mg of oil or grease in extract as determined from calibration curve.

6.   Precision

and Bias

Method C was used by a single laboratory to test a wastewater sample. By this method the oil and grease concentration was 17.5 mg/L. When 1-L sample portions were dosed with 14.0 mg of a mixture of No. 2 fuel oil and Wesson oil, the recovery of  added oils was 99% with a standard deviation of 1.4 mg. 7. Bibliography GRUENFELD , M. 1973. Extraction of dispersed oils from water for quantitative analysis by infrared spectrophotometry. Environ. Sci. Technol.   7:636.

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AGGREGATE ORGANIC CONSTITUENTS (5000)

5520 D. Soxhlet Extraction Method 1.

  General Discussion

Soluble metallic soaps are hydrolyzed by acidification. Any oils and solid or viscous grease present are separated from the liquid samples by  fi ltration. After extraction in a Soxhlet apparatus with solvent, the residue remaining after solvent evaporation is weighed to determine the oil and grease content. Compounds volatilized at or below 103°C will be lost when the  fi lter is dried. 2.   Apparatus

a. Extraction apparatus,  Soxhlet, with 125-mL extraction  fl ask. b. Extraction thimble,  paper, solvent-extracted. c. Electric heating mantle. d. Vacuum pump  or other source of vacuum. e. Vacuum filtration apparatus.  f. Buchner funnel,  12-cm. g. Filter paper,  11-cm diam.* h. Muslin cloth disks,  11-cm diam, solvent-extracted. i. Glass beads or glass wool,  solvent-extracted.  j. Water bath,  capable of maintaining 85°C. k. Distilling adapter   with drip tip. See 5520B.2i   and Figure 5520:1. l. Ice bath. m. Waste receptacle,  for used solvent. n. Desiccator .

ing of a muslin cloth disk overlaid with  fi lter paper. Wet paper and muslin and press down edges of paper. Using vacuum, pass 100 mL filter aid suspension through prepared filter and wash with 1 L distilled water. Apply vacuum until no more water passes filter. Filter acidi fied sample. Apply vacuum until no more water passes through filter. Using forceps, transfer entire filter to a watch glass. Add material adhering to edges of muslin cloth disk. Wipe sides and bottom of collecting vessel and Buchner funnel with pieces of  filter paper soaked in extraction solvent, taking care to remove all  fi lms caused by grease and to collect all solid material. Add pieces of  fi lter paper to material on watch glass. Roll all  fi lter material containing sample and  fi t into an extraction thimble. Add any pieces of material remaining on watch glass. Wipe watch glass with a filter paper soaked in extraction solvent and place in extraction thimble. Dry filled thimble in a hot-air oven at 103 °C for 30 min. Fill thimble with glass wool or small glass beads. Weigh extraction fl ask and add 100 mL extraction solvent (n-hexane, ¶ 3b). Extract oil and grease in a Soxhlet apparatus, at a rate of 20 cycles/h for 4 h. Time from first cycle. For stripping and recovery of solvent, cooling extraction  fl ask before weighing, and determining initial sample volume, see Section 5520B.4. 5.   Calculation

See Section 5520B.5.

3.   Reagents

6.   Precision

and Bias

a. Hydrochloric acid , HCl, 1  1. b.  n- Hexane:  See Section 5520B.3b. c. Diatomaceous-silica filter aid suspension,†   10 g/L distilled water.

In analyses of synthetic samples containing various amounts of Crisco and Shell S.A.E. No. 20 oil, an average recovery of  98.7% was obtained, with a standard deviation of 1.86%. Ten replicates each of two wastewater samples yielded standard deviations of 0.76 mg and 0.48 mg.

4.   Procedure

7. Bibliography

When sample is brought into the laboratory, either mark  sample bottle at the meniscus or weigh bottle for later determination of volume. If sample has not been acidi fied previously (see Section 5520A.3), acidify with 1:1 HCl or 1:1 H 2SO4  to pH 2 or lower (generally, 5 mL is suf ficient). Prepare  fi lter consist* Whatman No. 40 or equivalent. †  Hyflo Super-Cel, Manville Corp., or equivalent.

HATFIELD, W.D. & G.E. S YMONS. 1945. The determination of grease in sewage.  Sewage Works J.   17:16. GILCREAS , F.W., W.W. S ANDERSON   & R.P. ELMER. 1953. Two new methods for the determination of grease in sewage.   Sewage Ind. Wastes   25:1379. ULLMANN, W.W. & W.W. S ANDERSON . 1959. A further study of methods for the determination of grease in sewage. Sewage Ind. Wastes 31:8.

OIL & GREASE (5520)/Hydrocarbons

5-41

5520 E. Extraction Method for Sludge Samples 1.

  General Discussion

4.   Procedure

Drying acidified sludge by heating leads to low results. Magnesium sulfate monohydrate is capable of combining with 75% of its own weight in water in forming MgSO 4 7H2O and is used to dry sludge. After drying, the oil and grease can be extracted with  n -hexane. 

When sample is brought into the laboratory, if it has not been acidified previously (Section 5520A.3), add 1 mL conc HCl/80 g sample. In a 150-mL beaker weigh out a sample of wet sludge, 20  0.5 g, for which the dry-solids content is known. Acidify to pH 2.0 or lower (generally, 0.3 mL conc HCl is suf ficient). Add 25 g MgSO4 H2O. Stir to a smooth paste and spread on sides of beaker to facilitate subsequent sample removal. Let stand until solidified, 15 to 30 min. Remove solids and grind in a porcelain mortar. Add powder to a paper extraction thimble. Wipe beaker and mortar with small pieces of  filter paper moistened with solvent and add to thimble. Fill thimble with glass wool or small glass beads. Tare extraction flask, and add 100 mL n-hexane. Extract in a Soxhlet apparatus at a rate of 20 cycles/h for 4 h. If  any turbidity or suspended matter is present in the extraction flask, remove by  fi ltering through grease-free cotton into another weighed  fl ask. Rinse  fl ask and cotton with solvent. For solvent stripping and recovery, and cooling the extraction flask before weighing, see Section 5520B.4. 

2.   Apparatus

a. Beaker,   150-mL, glass. b. Mortar and pestle,  porcelain. c. Extraction apparatus, Soxhlet. d. Extraction thimble, paper, solvent-extracted. e. Glass beads or glass wool,  solvent-extracted.  f. Electric heating mantle. g. Vacuum pump  or other source of vacuum. h. Liquid funnel,  glass. i. Grease-free cotton:  Extract nonabsorbent cotton with solvent.  j. Water bath,  capable of maintaining 85°C. k. Distilling adapter   with drip tip. See 5520B.2i   and Figure 5520:1. l. Ice bath. m. Waste receptacle,  for used solvent. n. Desiccator .

5.   Calculation

Oil and grease as % of dry solids 

3.   Reagents

a. Hydrochloric acid , HCl, conc. b.  n- Hexane:  See Section 5520B.3b. c. Magnesium sulfate monohydrate:  Prepare MgSO4 H2O by drying a thin layer overnight in an oven at 150 °C. 

gain in weight of flask, g  100 weight of wet solids, g  dry solids fraction

6.   Precision

The examination of six replicate samples of sludge yielded a standard deviation of 4.6%.

5520 F. Hydrocarbons 1.

  General Discussion

Silica gel has the ability to adsorb polar materials. If a solution of hydrocarbons and fatty materials in a nonpolar solvent is mixed with silica gel, the fatty acids are removed selectively from solution. The materials not eliminated by silica gel adsorption are designated hydrocarbons by this test.

3.   Reagents

a. n- Hexane:  See Section 5520B.3b. b. Trichlorotri fl uoroethane:  See Section 5520C.3b. c. Silica gel,  100 to 200 mesh.†  Dry at 110°C for 24 h and store in a tightly sealed container. 4.   Procedure

2.   Apparatus

a. Magnetic stirrer. b. Magnetic stirring bars, TFE-coated. c. Liquid funnel,  glass. d. Filter paper,  11-cm diam.* e. Desiccator .

* Whatman No. 40 or equivalent.

Use the oil and grease extracted by Method B, C, D, E, or G for this test. When only hydrocarbons are of interest, introduce this procedure in any of the methods before final measurement. When hydrocarbons are to be determined after total oil and grease has been measured, redissolve the extracted oil and grease in trichlorotri fluoroethane (Method C)

†  Davidson Grade 923 or equivalent.

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AGGREGATE ORGANIC CONSTITUENTS (5000)

or 100 mL n-hexane (Method B, D, E, or G). To 100 mL solvent add 3.0 g silica gel/100 mg total oil and grease, up to a total of 30.0 g silica gel (1000 mg total oil and grease). For samples with more than 1000 mg total oil and grease use a measured volume of the 100 mL solvent dissolved sample, add appropriate amount of silica gel for amount of total oil and grease in the sample portion, and bring volume to 100 mL. Stopper container and stir on a magnetic stirrer for 5 min. For infrared measurement of hydrocarbons no further treatment is required before measurement as described in Method C. For gravimetric determinations, filter solution through filter paper pre-moistened with solvent, wash silica gel and filter paper with 10 mL solvent, and combine with  fi ltrate. For solvent stripping and recovery, and for cooling extraction flask before weighing, see Section 5520B.4.

and Bias

The following data, obtained on synthetic samples, are indicative for natural animal, vegetable, and mineral products, but cannot be applied to the specialized industrial products previously discussed. For hydrocarbon determinations on 10 synthetic solvent extracts containing known amounts of a wide variety of petroleum products, average recovery was 97.2%. Similar synthetic extracts of Wesson oil, olive oil, Crisco, and butter gave 0.0% recovery as hydrocarbons measured by infrared analysis. Using reagent water fortified with approximately 20 mg/L each of hexadecane and stearic acid, combined data from singlelaboratory studies and an interlaboratory method validation study yielded an average recovery of 89% and precision (as relative standard deviation) of 13%. 7. Bibliography

5.   Calculation

Calculate hydrocarbon concentration, in milligrams per liter, as in oil and grease (Method B, C, D, or G).

5520 G. 1.

6.   Precision

U.S. ENVIRONMENTAL PROTECTION AGENCY. 1995. Report of the Method 1664 Validation Studies. EPA-821-R-95-036, U.S. Environmental Protection Agency, Washington, D.C.

Solid-Phase, Partition-Gravimetric Method

  General Discussion

Dissolved or emulsified oil and grease is extracted from water by passing a sample through a solid-phase extraction (SPE) disk  where the oil and grease are adsorbed by the disk and subsequently eluted with  n -hexane. Some extractables, especially unsaturated fats and fatty acids, oxidize readily; hence, special precautions regarding temperature and solvent vapor displacement are provided. This method is not applicable to materials that volatilize at temperatures below 85 °C, or crude and heavy fuel oils containing a significant percentage of material not soluble in  n -hexane. This method may be a satisfactory alternative to liquid-liquid extraction techniques, especially for samples that tend to form dif ficult emulsions during the extraction step. 1 2.   Apparatus

a. SPE extraction apparatus, 90 mm.* b. Oil and grease SPE extraction disk,  90 mm.† c. Distilling  fl ask,  125 mL. d. Water bath,  capable of maintaining 85 °C. e. Vacuum pump  or other source of vacuum.  f. Distilling adapter  with drip tip. Setup of distillate recovery apparatus is shown in Figure 5520:1. Alternatively, use commercially available solvent recovery equipment. g. Ice bath. h. Waste receptacle,  for used solvent.

* SPE extraction apparatus is available from multiple vendors. Currently available equipment includes manual, semi-automated, and automated. †  SPE extraction disks are available from multiple vendors.

i. Desiccator. 3.   Reagents

a. Hydrochloric or sulfuric acid,  1:1: Mix equal volumes of  either acid and reagent water. b.  n- Hexane,  boiling point 69°C. The solvent should leave no measurable residue on evaporation; distill if necessary. Do not use any plastic tubing to transfer solvent between containers. c. Sodium sulfate, Na2SO4, anhydrous crystal. d. Acetone,  residue less than 1 mg/L. e. Methanol,  ACS grade.  f. Hexadecane,  98% minimum purity. g. Stearic acid,   98% minimum purity. h. Standard mixture,  hexadecane/stearic acid 1:1 w/w, in acetone at 2 mg/mL each. 4.   Procedure

When a sample is brought into the laboratory, either mark  sample bottle at water meniscus or weigh bottle, for later determination of sample volume. If sample has not been acidified previously (see Section 5520A.3), acidify with either 1:1 HCl or 1:1 H 2SO4  to pH 2 or lower (generally, 5 mL is suf ficient for 1 L sample). Assemble SPE extraction apparatus with oil and grease SPE disk installed and condition disk  according to apparatus and disk manufacturers’   instructions. Do not let disk dry before introducing sample for extraction. Conditioning is a critical step for uniform flow and good recovery. If the sample is high in suspended solids, decant liquid portion after allowing solids to settle. Extract sample at

PHENOLS (5530)/Introduction

an optimum flow rate of 100 mL/min; faster extraction rates will reduce recoveries. After extraction, ensure that the disk  dries fully before elution; however, use of an acetone rinse to aid in drying also will result in low recoveries. Carefully control vacuum during elution to let solvent fully penetrate the disk. A good-quality pump capable of controlling the vacuum from 20.3 cm (8 in.) Hg for elution to 63.5 cm (25 in.) Hg for disk drying will reduce variability of results. Pour sample into reservoir. If sample is high in suspended solids or sediment that may clog the disk, decant supernatant into reservoir first. Apply vacuum at an optimum  fl ow rate of 100 mL/min and add sediment-laden residual from decanted sample to reservoir before allowing disk to go dry. After sample extraction is complete, apply full vacuum for 10 min to remove as much residual water as possible from disk and then change receivers. Rinse sample container with a portion of  n-hexane and add solvent to reservoir, making sure that reservoir walls are rinsed in the process. Apply a slight vacuum to draw a few drops of  n-hexane through disk, then release. Let solvent soak disk for 2 min. Collect eluent by applying enough vacuum to cause a slow stream of hexane to drip through disk. Let disk dry before repeating elution with a second portion of  n-hexane. Pour combined eluent through a funnel containing a fi lter paper and 10 g Na2SO 4, both of  which have been solvent-rinsed, into a clean, tared distilling flask containing boiling chips. Rinse collection vial and  fi lter containing Na2SO4   with n -hexane, and add to boiling flask. Distill solvent from fl ask in a water bath at 85 °C. Fit distillation  fl ask with a distillation adaptor equipped with a drip tip and collect solvent in an ice-bath-cooled receiver (Figure 5520:1); reduce volume, cool, and weigh to constant weight as described in 5520B.4.

5.   Calculations

Calculate oil and grease in sample as follows:

5-43

mg oil and grease/L 

W 

r 

V 

s

where: total weight of  fl ask and residue, minus tare weight of  flask, mg, and V   initial sample volume, L.

W 

r 



s

6.   Precision

and Bias

In a comparison of laboratory-forti fied reagent water samples (n    46) with additions of approximately 20 mg/L each of  hexadecane and stearic acid and analyzed by both automated and manual SPE systems, recoveries of 87.1   7.8% and 92.5  4.4% recovery on 10% fortified reagent water samples.‡ Precision for wastewaters may vary by matrix. In a singlelaboratory testing replicate (n4 – 6) domestic wastewater samples (8 different samples) in the 18- to 60-mg/L range, the CV averaged 9.0%. Another laboratory testing replicates ( n  4) of  16 different types of wastewater in the 4- to 3000-mg/L range reported CVs ranging from 1.1 to 57.1% for 19 wastewater types; pooled results from four laboratories showed an average CV of 17.0%  13.8%.‡ Single-laboratory control charts for matrix known additions analysis showed an average relative percent difference of 2.2% and an average percent recovery of 87.2% with a standard deviation of 5.5%. Two laboratories were able to achieve an MDL of 1.4 mg/L, using either manual or semi-automated SPE apparatus. 7. Reference 1. U.S. ENVIRONMENTAL PROTECTION AGENCY. 1999. Method 1664, Revision A. EPA-821-R-98-002, U.S. Environmental Protection Agency, Washington, D.C.

‡   Data provided by USEPA/DynCorp Systems from the public comment docu-

ment on EPA Method 1664. Proposed Rule and Notice of Availability (62 Fed. Reg. 51621; FRL-5901-5).